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Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation

Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced d...

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Autores principales: Jih, Kang-Yang, Sohma, Yoshiro, Hwang, Tzyh-Chang
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457689/
https://www.ncbi.nlm.nih.gov/pubmed/22966014
http://dx.doi.org/10.1085/jgp.201210834
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author Jih, Kang-Yang
Sohma, Yoshiro
Hwang, Tzyh-Chang
author_facet Jih, Kang-Yang
Sohma, Yoshiro
Hwang, Tzyh-Chang
author_sort Jih, Kang-Yang
collection PubMed
description Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced dimerization of its two nucleotide-binding domains (NBD1 and NBD2), whereas gate closure is facilitated by ATP hydrolysis-triggered partial separation of the NBDs. This generally held theme of CFTR gating—a strict coupling between the ATP hydrolysis cycle and the gating cycle—is put to the test by our recent finding of a short-lived, post-hydrolytic state that can bind ATP and reenter the ATP-induced original open state. We accidentally found a mutant CFTR channel that exhibits two distinct open conductance states, the smaller O1 state and the larger O2 state. In the presence of ATP, the transition between the two states follows a preferred O1→O2 order, a telltale sign of a violation of microscopic reversibility, hence demanding an external energy input likely from ATP hydrolysis, as such preferred gating transition was abolished in a hydrolysis-deficient mutant. Interestingly, we also observed a considerable amount of opening events that contain more than one O1→O2 transition, indicating that more than one ATP molecule may be hydrolyzed within an opening burst. We thus conclude a nonintegral stoichiometry between the gating cycle and ATP consumption. Our results lead to a six-state gating model conforming to the classical allosteric mechanism: both NBDs and transmembrane domains hold a certain degree of autonomy, whereas the conformational change in one domain will facilitate the conformational change in the other domain.
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spelling pubmed-34576892013-04-01 Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation Jih, Kang-Yang Sohma, Yoshiro Hwang, Tzyh-Chang J Gen Physiol Article Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced dimerization of its two nucleotide-binding domains (NBD1 and NBD2), whereas gate closure is facilitated by ATP hydrolysis-triggered partial separation of the NBDs. This generally held theme of CFTR gating—a strict coupling between the ATP hydrolysis cycle and the gating cycle—is put to the test by our recent finding of a short-lived, post-hydrolytic state that can bind ATP and reenter the ATP-induced original open state. We accidentally found a mutant CFTR channel that exhibits two distinct open conductance states, the smaller O1 state and the larger O2 state. In the presence of ATP, the transition between the two states follows a preferred O1→O2 order, a telltale sign of a violation of microscopic reversibility, hence demanding an external energy input likely from ATP hydrolysis, as such preferred gating transition was abolished in a hydrolysis-deficient mutant. Interestingly, we also observed a considerable amount of opening events that contain more than one O1→O2 transition, indicating that more than one ATP molecule may be hydrolyzed within an opening burst. We thus conclude a nonintegral stoichiometry between the gating cycle and ATP consumption. Our results lead to a six-state gating model conforming to the classical allosteric mechanism: both NBDs and transmembrane domains hold a certain degree of autonomy, whereas the conformational change in one domain will facilitate the conformational change in the other domain. The Rockefeller University Press 2012-10 /pmc/articles/PMC3457689/ /pubmed/22966014 http://dx.doi.org/10.1085/jgp.201210834 Text en © 2012 Jih et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).
spellingShingle Article
Jih, Kang-Yang
Sohma, Yoshiro
Hwang, Tzyh-Chang
Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
title Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
title_full Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
title_fullStr Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
title_full_unstemmed Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
title_short Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
title_sort nonintegral stoichiometry in cftr gating revealed by a pore-lining mutation
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457689/
https://www.ncbi.nlm.nih.gov/pubmed/22966014
http://dx.doi.org/10.1085/jgp.201210834
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AT hwangtzyhchang nonintegralstoichiometryincftrgatingrevealedbyaporeliningmutation